A truck vehicle having a 6×2 configuration comprises right and left front steering wheels and a tandem rear axle which has a fore axle and an aft axle one of which is a drive axle and the other of which is a non-drive axle. Typically, the fore axle is the drive axle and the aft axle is the tag axle.
It is generally recognized within the trucking industry that a truck vehicle having a 6×4 configuration (both axles of a tandem rear axle being drive axles) provides better road traction than a truck vehicle having a 6×2 configuration. However, because a truck vehicle having a 6×2 configuration is lighter in weight, it can transport a heavier payload, and it can operate with better fuel economy not only because of its lighter weight, but also because its simpler powertrain has smaller energy losses. It is also generally recognized that a truck vehicle having a 6×2 configuration may be prone to uneven tire wear between tires on the drive axle and those on the tag axle. For mitigating issues involving fuel economy and tire wear, some truck vehicles which have a 6×2 configuration also have a mechanism which can be manually set while the vehicle is stopped to re-distribute weight borne by one of the tandem rear axles to the other.